The present invention relates to an oil filtering device for a motor bicycle and, more specifically, to an oil filtering device for use in a swing-type power unit of a scooter having a four-stroke-cycle engine.
FIG. 10 shows an engine 100 having a conventional oil filtering device 101 for a scooter. With this oil filtering device 101, a lubricating oil 102, the flow of which is indicated by arrows in an oil pan, is conveyed to a crank shaft 105 by an oil pump 104 immediately after any relatively large particles of dirt have been filtered out therefrom by an oil strainer 103, serving as a first filtering section, provided on the lower surface of the engine 100. Thereafter, the oil is conveyed to portions of the engine 100 at which a friction occurs, for example, a connecting rod 107 and a cylinder head 108, through centrifugal oil filter 106 provided on the crank shaft 105 and serving as a second filtering section. The mounting of the oil strainer, 103, which is detachably provided on the lower surface of the engine 100, is rather troublesome. Further, since the centrifugal oil filter 106 is formed on the crank shaft 105, its mounting is also rather troublesome.
Further, the crank shaft 105, on which the centrifugal oil filter 106 is provided, is subjected to strong vibrations during travelling, so that the oil 102 supplied to the crank shaft 105 is liable to be mixed with air, which results in that the lubricating performance of the lubricating oil 102 is liable to deteriorate.
In addition, since the centrifugal oil filter 106 is situated above and spaced apart from the oil strainer 103, the load on the oil pump 104 due to the weight of dust, dirt, etc. which has not been filtered out by the oil strainer 103 is considerably large, which also is not desirable from the viewpoint of the lubricating performance of the lubricating oil 102.